888
FXUS65 KBYZ 222341
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
541 PM MDT MON JUN 22 2026
KEY MESSAGES
- UNSETTLED TODAY. A FEW THUNDERSTORMS MAY BECOME STRONG TO SEVERE
MAINLY EAST OF BILLINGS. MAIN THREATS ARE HAIL AND LOCALLY HEAVY
RAINFALL.
- MOSTLY DRY AND SEASONABLY COOL TUESDAY.
- WARMER WITH A CHANCE FOR AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS WEDNESDAY AND THURSDAY. HIGHEST CHANCE FOR
PRECIPITATION AND A SEVERE STORM OR TWO WILL BE THURSDAY.
- A WARM AND MAINLY DRY DAY FRIDAY, WITH INCREASING CHANCES FOR
PRECIPITATION AND STRONG STORMS BY FRIDAY NIGHT.
- A STRONG WEATHER SYSTEM LOOKS INCREASINGLY LIKELY (MODERATE
CHANCE) TO BRING MORE WIDESPREAD PRECIPITATION AND MOUNTAIN
SNOW TO THE AREA OVER THE WEEKEND. STAY UP TO DATE WITH THE
LATEST FORECAST.
DISCUSSION
TODAY THROUGH MONDAY...
WEAK COLD FRONT IS CURRENTLY LOCATED FROM NEAR HYSHAM SOUTHWEST TO
NEAR BILLINGS, SAGGING INTO THE BEARTOOTH FOOTHILLS AROUND ROSCOE
LATE THIS MORNING. THE FRONT IS DIFFUSE AND IS MAINLY OUTLINED BY
WEAK CONVECTION ALONG AND AHEAD OF IT, AND A LOW CLOUD DECK
FILLING IN BEHIND IT WITH OVERCAST CONDITIONS FROM BILLINGS
NORTHWEST THROUGH HARLOWTON. THIS CLOUD COVER IS GOING TO WORK
AGAINST DAYTIME HEATING TODAY EVEN IF BREAKS DEVELOP AS EXPECTED
LATER TODAY, AND NORTHERLY WINDS OVER THIS AREA WILL BE PULLING
SOMEWHAT DRIER AIR SOUTHWARD. BOTH OF THESE FACTORS ALONG WITH A
LESS FAVORABLE SHEAR PROFILE WILL WORK AGAINST STRONG STORMS
FORMING IN THIS AREA, THOUGH NON-SEVERE SHOWERS AND THUNDERSTORMS
ARE STILL IN THE FORECAST. AHEAD OF THE FRONT THERE IS STILL
SUBSTANTIAL CLOUD COVER BUT ENOUGH BREAKS TO SEE TEMPERATURES INTO
THE LOW TO MID 70S WHICH ALONG WITH DEW POINTS IN THE 50S IS
EXPECTED TO PRODUCE 1000-2000J/KG OF CAPE THIS AFTERNOON.
CONVERGENCE ALONG THE FRONT ALONG WITH JET DYNAMICS PRODUCED BY AN
80-90KT WESTERLY JET STREAK WILL BE THE FORCING MECHANISM FOR A
FEW STRONG TO SEVERE STORMS THROUGH EARLY EVENING. BEST CHANCE FOR
A STRONG TO SEVERE STORM WILL BE ALONG AND SOUTH OF US-212 EAST OF
CROW AGENCY AND SOUTH ALONG I-90 THROUGH SHERIDAN COUNTY.
DIFFERENTIAL HEATING AND CONVECTIVELY COOLED AIR POOLING ON THE
COLD SIDE OF THE FRONT WILL ENHANCE NORTHERLY WINDS MID TO LATE
AFTERNOON PUSHING THE FRONT SOUTHWARD THROUGH THE FORECAST AREA BY
AROUND 8PM THIS EVENING WHICH WILL END THE SEVERE THREAT FOR OUR
AREA.
LOCALLY HEAVY RAINFALL IS POSSIBLE WITH STRONGER SHOWERS AND
THUNDERSTORMS TODAY AS PWAT VALUES ARE NEAR TO OVER AN INCH ACROSS
THE AREA. HOWEVER, THE FLASH FLOOD THREAT REMAINS LOW DUE TO THE
FASTER MOVEMENT OF THUNDERSTORMS TODAY WITH THE JET STREAM
OVERHEAD. WILL CONTINUE TO MONITOR CLOSELY BURN SCARS AND AREAS
THAT HAVE SEEN HEAVIER PRECIPITATION OVER THE PAST FEW DAYS FOR
POTENTIAL WARNINGS/ADVISORIES.
PRECIPITATION SHOULD EXIT THE AREA BY MIDNIGHT TONIGHT AS THE
COOLER DRIER NORTHERLY FLOW AND A 1025MB SURFACE HIGH SETTLE IN
OVERNIGHT. EXPECT A SUNNY AND MAINLY DRY DAY ON TUESDAY WITH
HIGHS FROM 65 TO 75 DEGREES AND PLENTY OF SUN. CAN'T RULE OUT A
FEW VERY LIGHT SHOWERS OVER THE HIGHER TERRAIN IN THE HEAT OF THE
DAY BUT NOTHING THAT SHOULD AFFECT ANY OUTDOOR PLANS.
RETURN LOW LEVEL MOISTURE FLOW ON WEDNESDAY WILL COMBINE WITH A
WEAK DISTURBANCE TO BRING A CHANCE (30% LOW ELEVATIONS/50% HIGH
ELEVATIONS) FOR SHOWERS AND THUNDERSTORMS TO THE SOUTHERN TIER OF
THE FORECAST AREA (SOUTH OF A LIVINGSTON TO BILLINGS TO EKALAKA
LINE). NCAR ML/AI PROGS SHOW A LOW CHANCE (5%) FOR A STRONG TO
SEVERE THREAT RIGHT ALONG THE MT/WY BORDER IN THE
AFTERNOON/EVENING HOURS WHILE THE CURRENT SPC DAY 3 OUTLOOK IS
HOLDING THE STRONGER STORM THREAT FURTHER SOUTH INTO WYOMING. THE
THUNDERSTORM TREND ON WEDNESDAY IS MORE ROBUST THAN IT WAS 24
HOURS AGO, SO WILL HAVE TO KEEP AN EYE ON THE MOISTURE RETURN
(CAPE) AND SOUTHEASTERLY WIND DEVELOPMENT (SHEAR) OVER THE NEXT 48
HOURS TO SEE IF THE INGREDIENTS CONTINUE TO TREND MORE FAVORABLE
FOR STRONGER STORMS.
THURSDAY IS TRENDING MORE FAVORABLE FOR WIDESPREAD SHOWERS AND
THUNDERSTORMS (40-80% CHANCE). A STRONG STORM SYSTEM OFF THE WEST
COAST WILL INDUCE RIDGING ALONG THE SPINE OF THE ROCKIES WHICH
WILL ALLOW FOR STRONGER LOW LEVEL SOUTHEASTERLY WINDS TO DEVELOP
AS A STRONG THERMAL LOW DEVELOPS WEST OF THE DIVIDE. THESE
SOUTHEASTERLY WINDS WILL BE TAPPING SUBSTANTIAL LOW LEVEL PLAINS
MOISTURE, PULLING IT INTO THE AREA AND BOOSTING PWATS OVER 1.25
INCHES BY MID DAY THURSDAY. THE SOUTHWEST WINDS ALOFT AND
SOUTHEAST AT THE SURFACE WILL PROVIDE PLENTY OF SHEAR TO SUPPORT
ROTATING UPDRAFTS AND THE MOISTURE WILL PROVIDE PLENTY OF CAPE IF
TEMPERATURES ARE WARM ENOUGH. THE QUESTION WILL BE WILL
TEMPERATURES GET WARM ENOUGH TO SUPPORT ROBUST CONVECTION AS THE
CURRENT FORECAST SHOWS SUBSTANTIAL CLOUD COVER STARTING IN THE
PRE-DAWN HOURS. A DISTURBANCE PUSHING OVER THE RIDGING TO THE
WEST AND SLIDING SOUTHEAST INTO THE PLAINS WILL BE THE MAIN
TRIGGER FOR SHOWERS AND STORMS. ALL THE INGREDIENTS ARE PRESENT,
JUST NEED ENOUGH CLOUD BREAKS TO GET SOME HEATING. NCAR ML/AI
GUIDANCE SHOWS UP TO A 30% CHANCE FOR SEVERE THUNDESTORMS
THURSDAY, HIGHEST CHANCES ALONG AND SOUTH OF I-94. AS IT STANDS
THE CURRENT FORECAST SHOWS WIDESPREAD 0.2 TO 0.5 INCH
PRECIPITATION AMOUNT ACROSS THE AREA THROUGH THURSDAY EVENING.
FRIDAY IS AN INTERESTING DAY WITH STRONGER SOUTHWEST FLOW ALOFT
DRAGGING IN HOT DRY AIR FROM THE GREAT BASIN, WHILE LOW LEVEL
SOUTHEASTERLY WINDS KEEP MOIST AND SLIGHTLY COOLER AIR FILTERING
IN AT THE SURFACE. THIS SCENARIO RESULTS IN A STRONG INVERSION
ABOUT 10KFT AND CAPS OFF CONVECTION DURING THE DAY. MODELS ARE
SHOWING A DECENT AMOUNT OF CLOUD COVER DURING THE DAY. LATEST NBM
HIGH TEMPERATURE FORECAST IS ABOUT 5 TO 7 DEGREES COOLER THAN
YESTERDAYS FORECAST IN THE LOW 90S. IF THE INVERSION BREAKS OR THE
SOUTHWEST WINDS OVER THE MOUNTAINS CAN MECHANICALLY MIX THE
ATMOSPHERE SOME, TEMPERATURES COULD DEFINITELY BE WARMER WITH
GUSTIER SOUTHWEST WINDS ARRIVING AT THE SURFACE. BUT THE LATEST
TRENDS ARE COOLER, WITH MORE CLOUD COVER BUT STILL MAINLY DRY FOR
THE DAY INTO THE EARLY EVENING FRIDAY.
A STRONG STORM SYSTEM BEGINS TO IMPACT THE AREA FRIDAY NIGHT AS
COOLER AIR ALOFT WILL BREAK THE CAP AND ALLOW FOR CONVECTION TO
GET GOING. PRECIPITATION CHANCE PUSH INTO THE 30 TO 60% RANGE BY
MID EVENING, SPREADING WEST TO EAST ACROSS THE AREA. GUIDANCE
SUGGESTS A 10 TO 30% CHANCE FOR SEVERE STORMS OVERNIGHT.
THE WEEKEND INTO EARLY NEXT WEEK CONTINUES TO ADVERTISE A STRONG
PACIFIC STORM SYSTEM LINGERING SEVERAL DAYS OVER THE AREA.
PRECIPITATION CHANCES IN THE 40 TO 80% LAST FROM SATURDAY INTO
MONDAY AT THIS POINT, WITH SUGGESTIONS BY LONGER RANGE MODELS THAT
THE SYSTEM COULD PERSIST INTO TUE/WED. IN ADDITION TO WIDESPREAD
RAINFALL AND THUNDERSTORMS, TEMPERATURES COOL ENOUGH THAT
ACCUMULATING SNOW IS BEING ADVERTISED ABOVE 8000 FEET IN OUR
MOUNTAINS BY SUNDAY, LASTING INTO MONDAY. THIS WOULD IMPACT TRAVEL
OVER THE BEARTOOTH HIGHWAY AND MAY REQUIRE SOME WINTER HIGHLITES.
THERE IS STILL A LOT OF TIME FOR CHANGES TO THE FORECAST WITH
THIS SYSTEM. IF YOU HAVE OUTDOOR PLANS FOR THE WEEKEND, PLEASE
STAY UP WITH THE LATEST FORECAST THIS WEEK TO GET THE RELEVANT
DETAILS. CHAMBERS
AVIATION
ISSUED 2330Z. SCATTERED THUNDERSTORMS CAPABLE OF PRODUCING STRONG
WIND GUSTS AND LOCAL MVFR/IFR IN HEAVY RAIN W/ POSSIBLE HAIL WILL
IMPACT AREAS EAST OF KSHR-KMLS UNTIL ~03Z THIS EVENING. TO THE
WEST WILL BE SCATTERED SHOWERS AND A FEW WEAK THUNDERSTORMS. IN
ADDITION TO THE CONVECTIVE WINDS, A FRONTAL PASSAGE WILL BRING
N-NE 15-30KT GUSTS FOR A FEW HOURS THIS EVENING. LOCAL MVFR
CEILINGS ARE EXPECTED CLOSE TO THE FOOTHILLS AS WELL. EXPECT A
TRANSITION TO WIDESPREAD VFR BY EARLY TUESDAY. NW WINDS WILL GUST
15-25KTS EAST OF KBIL TOMORROW AFTERNOON. JKL
PRELIMINARY POINT TEMP/POPS
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 049/074 052/075 053/077 053/084 058/075 052/068 049/070
40/U 01/B 16/T 42/T 48/T 85/T 44/T
LVM 043/070 046/074 046/075 046/081 048/069 041/060 039/064
30/U 01/B 38/T 42/T 59/T 97/T 66/T
HDN 047/074 048/075 051/078 051/085 057/077 050/070 047/071
30/U 02/W 17/T 51/B 48/T 85/T 54/T
MLS 049/072 047/072 050/076 052/080 057/078 053/070 050/070
40/U 01/B 04/T 61/B 56/T 66/T 55/W
4BQ 050/072 047/071 050/073 052/079 057/079 053/070 050/071
60/U 03/W 27/T 71/B 46/T 85/T 55/T
BHK 046/069 043/071 044/073 049/075 052/077 050/071 047/070
60/N 00/B 03/T 62/W 46/T 85/T 55/T
SHR 046/068 045/071 047/074 047/082 053/076 046/068 043/070
63/B 16/T 59/T 61/B 37/T 86/T 54/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...SEVERE THUNDERSTORM WATCH 376 IN EFFECT UNTIL 8 PM MDT THIS
EVENING FOR ZONES 31>33-36-37-57-58-138-139-169-171.
WY...SEVERE THUNDERSTORM WATCH 376 IN EFFECT UNTIL 8 PM MDT THIS
EVENING FOR ZONES 198-199.
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